6.3.c

#include <stdio.h>
#include <sys/time.h>
#include <unistd.h>
#include <stdlib.h>

int main()
{
    int pi1[2];
    int pi2[2];
    char buf1[30], buf2[30];
    int p1 = pipe(pi1);
    int p2 = pipe(pi2);
    long temptime;
    struct timeval start, end;
    int i;
    if (p1 < 0 || p2 < 0)
    {
        fprintf(stderr, "pipe failed");
        exit(1);
    }
    int rc = fork();
    for (i = 0; i < 10; ++i)
    {
        if (rc < 0)
        {
            fprintf(stderr, "fork failed");
            exit(1);
        }
        else if (rc == 0)
        {
            read(pi1[0], buf1, 25);
            gettimeofday(&end, NULL);
            printf("%d\n", end.tv_usec - atol(buf1));
            gettimeofday(&start, NULL);
            sprintf(buf2, "%ld", start.tv_usec);
            write(pi2[1], buf2, 25);
        }
        else
        {
            gettimeofday(&start, NULL);
            sprintf(buf1, "%ld", start.tv_usec);
            write(pi1[1], buf1, 25);
            read(pi2[0], buf2, 25);
            gettimeofday(&end, NULL);
            printf("%d\n", end.tv_usec - atol(buf2));
        }
    }
    return 0;
}